Abstract
Navarretia divaricata, endemic to western North America and most recently considered a single species with two subspecies, was re-examined in light of field work, DNA sequences, comparative morphology, and a review of herbarium specimens including types. From these studies, we lectotypify the material on which N. divaricata is based, elevate N. divaricata subsp. vividior, which is an allotetraploid, to species rank (as N. vividior comb. et stat. nov.), and recognize three additional species: N. modocensis sp. nov., N. aeroides sp. nov., and N. torreyella sp. nov. Navarretia modocensis, the diploid paternal progenitor of N. vividior, is morphologically cryptic with respect to its allotetraploid offspring and difficult to distinguish on herbarium sheets. Navarretia aeroides, the diploid maternal progenitor of N. vividior, is nearly cryptic, but more easily distinguished from both N. modocensis and N. vividior by its smaller, more glandular inflorescences. Navarretia torreyella is readily distinguished from all of these species, but has been generally mistaken for N. divaricata subsp. vividior given its colored corolla tube and rare co-occurrence with the other vividior-like species. Conservation assessments, an identification key, and table of comparative morphological features are provided for each species, emended descriptions for N. divaricata and N. vividior, and a discussion of the syntypes for Gilia divaricata Torr. ex A.Gray.
Highlights
Multiple criteria applied to assess the presence of homogenizing gene flow under the framework of the unified species concept has provided strong evidence for the existence of previously unrecognized lineages in Polemoniaceae, including in Navarretia (Johnson and Cairns-Heath 2010, Johnson et al 2012, 2013, 2016)
Stemming from observations that N. divaricata subsp. divaricata does not form a monophyletic group with N. divaricata subsp. vividior in comparative DNA sequence analyses (Johnson et al 2016), that the two taxa co-occur without signs of hybridization, and that material assigned to N. divaricata subsp. vividior is polymorphic, we initiated fieldwork, a comprehensive review of herbarium specimens, and investigation of morphological and molecular variation across the geographic ranges of these taxa
The nrITS sequence matrix consisted of 37 terminals with two populations of N. vividior represented by distinct sequences recovered after cloning the original PCR fragments; the remaining four populations of N. vividior provided clean reads from direct sequencing of the original PCR products and were not cloned
Summary
Multiple criteria applied to assess the presence of homogenizing gene flow under the framework of the unified species concept (de Queiroz 2007) has provided strong evidence for the existence of previously unrecognized lineages in Polemoniaceae, including in Navarretia (Johnson and Cairns-Heath 2010, Johnson et al 2012, 2013, 2016). Stimulated by a need for nomenclatural housekeeping along with observations of variation in both morphological and molecular data, we here delimit several near-cryptic species from what previously has been considered a single species, Navarretia divaricata Greene. Within Navarretia Ruiz & Pav., N. divaricata is one of the more widely distributed species with populations extending from central California (and adjacent Nevada) to Idaho and British Columbia. It is one of the smallest-flowered Navarretia. Vividior merits recognition at the species level, and that four evolutionarily unique lineages exist in the material heretofore generally referred to subsp.
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